Those new Smash Bros. mystery characters are Lucina and Robin from Fire Emblem

Today, Nintendo was set to tease a "New Fighter Intro Video" at 7AM PST, and tease they did. The new fighter was revealed to be none other than Lucina from Fire Emblem: Awakening. But wait, there's more! Robin from Fire Emblem is also in, and he has a female gender swapped costume! Chrom was revealed as well, but it isn't clear if he is a playable character or just a skin/assist trophy/Final Smash, but all signs point to the latter.

Finally, Captain Falcon was revealed as a returning fighter. That's three confirmed characters with two new additions and one returning character (we'll see what Chrom is soon enough). Sakurai noted last week that they were "nearing the bottom of the stash" in terms of new announcements, so I wouldn't expect a whole lot more.